A plasma etching device is a device for etching an object such as a semiconductor wafer by generating plasma in a vacuum chamber. A placing table for placing the object, and an upper electrode arranged opposite to the placing table are provided inside the vacuum chamber. A lower electrode is provided in the placing table. Further, a hole (a gas introduction hole) for introducing gas into the vacuum chamber is provided in the upper electrode. During treating the object, gas is introduced into the vacuum chamber from the hole, and the object is etched by applying a high-frequency voltage between the lower electrode and the upper electrode to generate plasma.
The etching fine processing of a semiconductor element by using low temperature plasma in this device is also referred to as dry etching. The dry etching is a process for a semiconductor element. The dry etching is a process for providing a pattern of grooves or holes to a silicon/insulating material film (for example, SiO2, PSG, BPSG)/a metal film (for example, Al, W, Cu) etc., with plasma of reactive gas by using a photoresist pattern as a mask, wherein the photoresist pattern is on a film to be etched which has been cured after photolithography. Thus, the fine processing is performed accurately in accordance with the pattern formed by a lithographic equipment.
Etching gas is introduced into a vacuum chamber in accordance with the film to be etched, and plasma is generated by applying a high-frequency to perform the dry etching. The dry etching is performed through a step of reactive ion etching (RIE: Reactive Ion Etching), in which a region not covered with a resist (mask material) is cut by ion collision.
The ion generated by plasma discharge is subjected to a surface chemical reaction with the film to be etched on a silicon wafer, and the dry etching is conducted by vacuum evacuating the product. After this process, the organic matter of the resist is burned by ashing process. In the case where the dimension of the fine pattern is close to the thickness of the film to be etched, RIE is employed.
This dry etching is the mainstream in the formation of semiconductor element currently. Especially, in the ultra-fine processing of a semiconductor element using a silicon wafer with a size of 300 mm (millimeter), the degree of integration is increased, and the pitch of the line width (Line) and the line space (Space) becomes severe. Therefore, an improvement in the processing characteristics, the yield, and the productivity of the dry etching is further required.
The design rule of the CMOS semiconductor element tends to advance the gate length from 14 nm (nanometer) to 9 nm, and to make the line width and the line space of the etching severe similarly. In the manufacture of such semiconductor element, not only the dimensional accuracy of the pattern, but also the corrosion of the pattern, the dust emission, the damage due charge-up, the change with time and the like, are problems which should be overcome. Furthermore, a technique is desired for controlling the generated plasma by introducing reaction gas which is applicable to a larger diameter of the wafer.
The processing accuracy, the pattern shape, the etching selection ratio, the processing uniformity in the wafer surface, the etching rate and the like are important factors in the dry etching. For example, in order to make the processing cross-sectional surface of the pattern formed by dry etching vertical, a deposition film which is referred to as a side wall protection film should not be too thick. Further, when there is a film thickness variation in the side wall protection film, it will be the cause of the dimension variation. Therefore, techniques such as an ideal low-temperature etching which does not require a side wall protection film are important. Moreover, formation of insufficient side wall protection film at the bottom portion of the pattern, particles migrating on the surface, temperature of the surface, gas flowing at the bottom portion and the like should also be considered.
Further, with respect to the etching uniformity, the flowing of the reaction gas, the uniformities of various conditions such as the plasma uniformity, the bias uniformity, the temperature uniformity, the uniformity of reaction product redeposition and the like are important. Especially, with respect to the wafer of large diameter (for example, size of 300 mm), the non-uniformity of reaction product redeposition has a large effect for the uniformity of the etching processing.
In order to reduce the cost of plasma etching device or etching treatment, the running cost reduction and the like is required, wherein the running cost reduction is resulted from an efficient plasma treatment, a consecutive treatment, and life elongation of components. How to realize the processing defective reduction, the seasoning time reduction, the high operation rate (low failure rate), the maintenance frequency reduction etc., is a problem for obtaining an efficient plasma treatment technique or a high throughput, Especially, the upper electrode of the plasma etching device is a component which is consumed together with etching treatment. Accordingly, a technique of nondestructively monitoring the state of the upper electrode which varies together with the etching treatment, the state of the gas introduction hole, the state of the electrode when not being used, and the state before and after use, is very important for solving various problems of the dry etching.
Here, to manufacture an upper electrode in the plasma etching device, for example, a gas introduction hole is formed in a silicon monocrystal disk by a drilling processing with a diamond drill. In patent document 1, a cleaning method is disclosed. The cleaning method applies a surface treatment to the configuration component (for example, a shower head portion having gas injection holes, or an upper electrode) of the treatment device by using etching solution. In this technique, such as burrs generated during drilling processing are removed, and the surface of the configuration component is flattened.
The inner diameter of the gas introduction hole provided in this upper electrode is about 200 μm (micrometer) to 500 μm, which is very small. In addition, since it is necessary to go through the plate thickness, the length of the gas introduction hole is often greater than 10 mm. When such gas introduction hole is not accurately formed, the gas required by plasma etching cannot be uniformly introduced into the chamber, and the treatment of the object is likely to become uneven in the surface. In recent years, object such as a wafer has increased in size, and forming a number of gas introduction holes with high accuracy has become very important.
Here, it is very difficult to measure the state of the elongated gas introduction hole provided in the upper electrode nondestructively. For this reason, the lifetime of the upper electrode is not managed by the state of gas introduction hole, but is managed according to the using time. In other words, the relationship between the using time and the particle generation amount of the upper electrode is obtained as data in advance. According to the data, when the using time has become the time at which the particle generation amount exceeds the allowable range, it is determined that the lifetime of the upper electrode has ended.